Plant species richness and composition in a trans-Himalayan inner valley of Manang district, central Nepal

Abstract

Species richness normally decreases with increasing elevation. However, a hump and a plateau have been documented in species richness curves in the Nepal Himalaya. We sampled species richness and composition in 80 plots located in the north and south aspects of the dry valley of Manang, a trans-Himalayan inner valley of Nepal, between 3000 and 4000 masl. We used regression and ordination to relate species richness and composition to the physical environment. Pinus wallichiana, Juniperus indica, Abies spectabilis, Betula utilis and Salix species are the dominant tree species. B. utilis is found only in the moist north aspect and Juniperus species are more common in the dry south aspect. Moisture is the most important determinant of species richness and composition. At the local level, our results show a plateau in species richness at the elevation range of 3000–4000 masl. There were significantly more species on the north aspect than on the south. 
 
 Key words: aspect, altitude, beta-diversity, ordination, species richness, soil moisture 
 
 Himalayan Journal of Sciences Vol.4(6) 2007 p.57-64